Blood Vessels Flashcards
Describe the structure of a blood vessel
tunica interna: an endothelium that lines the interior of blood vessel and is exposed to blood. It secretes chemicals for dilation or constriction
tunica media: middle layer that is composed of smooth muscle, collagen, and elastic tissue. This layer strengthens vessels, regulates vessel diameter, and prevents blood pressure from bursting them
tunica externa: outer layer that consists of loose tissue that merges with other vessels, nerves and organs. This anchors the vessels
Vaso vasorum: small vessels that supply blood to larger vessels
Describe the types of arteries
Elastic arteries: consist of lots of elastic connective tissue and a major pressure reservoir. Ex: aorta and common carotid arteries
Muscular arteries: thick tunica media (smooth muscle) that goes to organs and muscle groups. Ex: brachial, femoral, and renal arteries
Arteriole arteries: big tunica media to lumen size ratio (muscular for its size). It controls the perfusion of bloof to specific organs
Describe the types of capillaries
Continuous capillaries: overlapping endothelial cells for diffusion of solutes. Ex: skeletal muscle, tissue, and blood/brain barrier
Fenustrated capillaries: pores present on endothelial cells and it acts as a filtration membrane. Ex: capillaries of kidneys
Sinusoid capillaries: large holes on endothelial cells that are widely spaced for large molecules to enter/exit. Ex: liver, red bone marrow.
*Capillary beds are networks of 10-100 capillaries
Describe veins
-veins have greater capacity for blood volume than arteries
-thinner walls, flacid, less muscular, and has elastic tissue.
-steady blood flow
-lower blood pressure
-converges to large veins until it reaches the heart
Varicose veins are veins that have been overstretched
What is the general route taken by blood?
- Begin at heart
- arteries
- arterioles
- capillaries (1 set)
- venules
- veins
- heart
Briefly describe circulatory routes
-venous anastomosis: most common where one vein empties into another
-arterial anastomosis: two arteries merge and provides alternative(collateral) routes of blood supply to tissue. This is coronary circulation and common around joints.
Explain the relationship between blood pressure, resistance, and flow
-blood supply is both the terms of flow and perfusion
-Blood flow: amount of blood flowing through an organ, tissue or vessel (ml/min)
-perfusion: flow per given volume or mass of tissue in a time (ml/min/g)
Cardiac output is equal to total blood flow at rest
How is blood pressure expressed?
Blood pressure is the force that blood exerts against vessel walls
Systolic pressure: peak arterial blood pressure taken at ventricular contraction (120)
Diastolic pressure: minimum arterial blood pressure taken at ventricular contraction between beats (75)
Normal Value: 120/75 mmHg
Blood pressure is determined by cardiac output, blood volume and resistance to flow
What are three factors that determine resistance to blood flow?
Peripheral resistance is the opposition to flow that blood encounters away from the heart
Blood viscosity: RBC count and albumin concentration elevates it the most; it can increase or decrease viscosity flow
Vessel length: the farther it flows through the vessel, the slower it flows. Pressure and flow decline with distance
Vessel Radius: most powerful influence over flow and the only way of controlling resistance.
-this is done through vasoreflexes that causes changes in vessel radus.
-Vasoconstriction: smooth muscle of tunica media contracts
_Vasodilation: relaxation of smooth muscle which allows blood pressure to increase vessel
How does vessel diameter influence blood pressure and flow?
The purpose of dilation and constriction is to control blood pressure and reroute blood from one body region to another. This is the general method of raising or lowering blood pressure through the body.
Ex:
-exercise dilates arteries in lungs, heart and muscles and vasoconstriction occurs in kidneys and digestive tract
-sleeping after eating causes vasoconstriction due to redirection of blood from lower limbs (raises BP) to intestinal arteries.
Local control influence on vessel diameter
Autoregulation is the ability of tissues to regulate their own blood supply. Vasoactive chemicals are substances secreted by platelets, endothelial cells and perivascular tissue to stimulate vasomotor responses
Neural Control Influence on Vessel Diameter
Central and autonomic immune systems exert control. Vasomotor center of medulla exerts sympathetic control over blood vessels.
Barioreflexes govern short term regulation of BP.
Hormonal Control Influence on Vessel Diameter
Angiotension 2 is a hormone that is a vasoconstrictor. It raises BP, promotes sodium water retention in kidneys, and increases blood pressure volume
Atrial natiuretic peptide increases sodium excretion in urine and decreases blood volume, blood pressure and causes vasodilation.
Anti-diuretic hormone promotes water retention, increases BP and is also a vasoconstrictor
How do materials from blood get to surrounding tissues?
Capillary exchange is a 2 way movement of fluid across capillary walls.
Diffusion: substances move across a capillary wall through filtration pores and intracellular clefts. This is passive transport. Ex: glucose and oxygen leave blood while CO2 and waste diffuse into blood
Filtration and Reabsorption: fluid filters out of the arerial end of capillary and osmotically reenters at the venous end so that materials get to the cell and metabolic wastes leave
-85% of fluid reenters vein and 15% of fluid enters lymphatic capillary
How can capillaries give off and reabsorb fluids?
Blood hydrostatic pressure drives fluid out of capillary where the arterial end has a bigh blood pressure and it is lower on the venous end.
Colloid osmotic pressure draws fluid into capillaries through a concentration gradient and results from albumins being more present in blood.
